KR100668910B1 - Apparatus and method for sharing reference clock of mobile terminal using global positioning system - Google Patents

Abstract

The present invention is a reference clock sharing apparatus of a mobile terminal using a global positioning system, processing a mobile communication system, calculates the amount of change of frequency according to the frequency change, and calculates the calculated value according to the calculated amount of frequency change system reference clock And a communication system processor for outputting to the GPS processor, a GPS signal, a process according to the received signal, an operation value according to the frequency change amount from the communication system processor, and a frequency according to the operation value. And a GPS processing unit for performing a calculation for compensation and compensating for a frequency by a value according to the calculation.

Description

Apparatus and method for sharing reference clock of mobile terminal using global positioning system {APPARATUS AND METHOD FOR SHARING A TCXO OF MOBILE TERMINAL USING GLOBAL POSITIONING SYSTEM IN MOBILE COMMUNICATION SYSTEM}

1 is a block diagram of an entire mobile terminal having a conventional GPS receiver.

2 is a view for explaining a reference frequency error of a reference clock of a conventional mobile terminal.

3 is a block diagram of an entire mobile terminal having a GPS receiver according to an exemplary embodiment of the present invention.

4 is a block diagram showing an important part of FIG.

5 is a view for explaining a reference frequency error of a reference clock of a mobile terminal according to an embodiment of the present invention.

6 is a flowchart illustrating a sharing operation of a reference clock of a mobile terminal according to an exemplary embodiment of the present invention.

The present invention relates to a global positioning system (GPS), and more particularly, to an apparatus and method for sharing a reference clock of a mobile terminal having a GPS function.

Currently, there are GPS satellites on Earth's orbit that broadcast their own exact ephemeris and system time as they rotate along a defined orbit, allowing GPS receivers on Earth to determine their position. The GPS receiver determines the exact time and its position by calculating the relative reception times of the GPS signals transmitted simultaneously from at least four GPS satellites. On the other hand, the GPS receiver as described above uses an assisted GPS ('AGPS') method and an autonomous mode or a standalone mode. In particular, the stand-alone or stand-alone method is a GPS receiver does not receive information for satellite signal acquisition in the mobile communication base station, the Assisted GPS, received from the server (AGPS method), and independently acquires the satellite signal directly from the GPS satellites In addition, by tracking and decoding the obtained signal for a long time, the orbital information of each satellite is obtained, and the position of the GPS receiver is calculated using the information.

Here, the AGPS server is a server connected to the CDMA network to provide a location service of the mobile terminal, and includes a reference GPS receiver and a computing device. The reference GPS receiver continuously tracks and monitors each GPS satellite signal, and provides calculation results and the like for the information necessary for the positioning service of the mobile terminal and the position of the measurement value obtained from the mobile terminal. In addition, the communication protocol between the AGPS server and the mobile terminal follows the IS-801 international standard.

As described above, when the GPS receiver operates in a standalone or standalone manner, a phase lock on a received GPS signal is required to demodulate navigation data including navigation information. It must be maintained for a long time. In addition, in order to maintain the phase lock on the GPS signal, a temperature compensated crystal (TCXO) oscillator (TCXO) of the GPS receiver is generally not influenced by another system during the corresponding time and the frequency should not change significantly.

As a result, since the GPS operation unit and the communication modem share the reference clock, the mobile terminal is configured to operate in a switching mode, so that the communication modem controls the reference clock during the GPS independent operation. That is, the operation of the automatic frequency control (hereinafter referred to as 'AFC') should be stopped. However, in the prior art, there is a problem in that the AFC function cannot be maintained for a long time for the normal operation of the communication modem.

1 is a view showing a schematic embodiment of a receiver structure of a mobile terminal using GPS according to the prior art. Before describing FIG. 1, the civil satellite signal of the GPS system as described above is typically modulated with a navigation data bit of 20 ms in a Coarse Acquisition (hereinafter, 'C / A') code of 1 ms. is modulated. The modem reference clock TCXO 101 is a TCXO capable of controlling a frequency value by the AFC unit 105. Meanwhile, as illustrated in FIG. 1, the GPS receiver of the mobile terminal measures the relative arrival time of GPS satellite signals received from at least four or more GPS satellites, that is, the C / A code delay. Determine the exact current time and location of the receiver, for example, the mobile terminal. In this case, in order for the GPS receiver to directly obtain a position, the GPS receiver should have satellite orbit information (Ephemeris) such as current position and speed information of each satellite.

As described above, when the GPS receiver operates in an autonomous mode or a standalone mode, the GPS receiver directly demodulates the navigation data contained in the satellite signal using the above information, for example, satellite orbit information. You will get it. As described above, the GPS receiver directly demodulates and acquires the navigation data contained in the satellite signal, and the navigation data demodulator 114 is 20 ms from the satellite signal detected by the signal detector 113 of FIG. 1. The navigation data bits, which are the navigation information of the period, are continuously demodulated for about 30 seconds and decoded to obtain orbit information of each satellite. At this time, in order to accurately demodulate the GPS navigation data, a phase lock is performed on a GPS signal received by controlling the carrier NCO 108 in a carrier-phase tracking loop of the GPS receiver. It is necessary to keep the lock correctly.

On the other hand, the GPS receiver embedded in the mobile terminal can improve the reception sensitivity of the GPS signal by sharing the absolute time and the reference clock (TCXO) of the CDMA system, and at the same time, the cost and size of the mobile terminal can be reduced by reducing the number of components. have. However, when the reference time (TCXO) is shared as described above, when the operation of controlling the reference clock according to the base station signal received from the CDMA mobile terminal (AFC) is in progress, as shown in the AFC operation section in FIG. Since the reference frequency of the field of view VCTXCO changes rapidly, the carrier-phase generated by the carrier loop filter 108 inside the GPS baseband processor 107 is affected. In addition, since the carrier phase is affected as described above, the phase lock is not maintained in the carrier phase tracking loop, which makes it impossible to accurately demodulate the navigation data.

When performing the GPS operation using the independent method or the standalone method as described above, the navigation data must be continuously demodulated for 30 seconds or more. In the case where the reference clock is shared in such a situation, when the control of the reference clock stops for a long time as described above, for example, for 30 seconds or more, the reference frequency of the reference clock as shown in FIG. It will drift slowly. As a result, there is a problem that the CDMA communication modem does not operate normally.

Accordingly, an object of the present invention is to provide an apparatus and method for sharing a reference clock with a communication system when a GPS operation unit embedded in a mobile terminal operates in a standalone or standalone manner in a mobile communication system.

Still another object of the present invention is to improve GPS performance and reduce manufacturing cost by sharing a reference clock with a communication system when the GPS operation unit embedded in the mobile terminal operates in a standalone or standalone manner in a mobile communication system. The present invention provides an apparatus and method.

An apparatus according to an embodiment of the present invention for achieving the above object is a reference clock sharing device of a mobile terminal using a global positioning system, processing the mobile communication system, and calculates the amount of change in frequency according to the frequency change And a communication system processor for outputting an operation value corresponding to the calculated frequency change amount to a system reference clock and a GPS processor, receiving a GPS signal, executing a process according to the received signal, and executing the frequency from the communication system processor. And a GPS processor for receiving a calculation value according to the change amount, executing a calculation for frequency compensation according to the calculation value, and compensating for a frequency with the value according to the calculation.

The method according to an embodiment of the present invention for achieving the above object in the reference clock sharing method of the mobile terminal for the global positioning system, the frequency of the communication system to detect the change in the magnitude of the value and the frequency change Comparing a predetermined threshold value, calculating a value according to the frequency change according to the comparison result, adjusting a frequency value of a system reference clock according to the calculation result, and performing an automatic frequency control operation. And synchronizing the reference clock to the base station signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific details such as specific components are shown, which are provided to help a more general understanding of the present invention, and it is understood that these specific details may be changed or changed within the scope of the present invention. It is self-evident to those of ordinary knowledge in Esau.

3 is a block diagram of the entire mobile communication terminal including a GPS receiver according to the present invention. Referring to FIG. 3, a mobile communication terminal according to the present invention includes an antenna 200 for transmitting and receiving a data signal with a base station or a GPS satellite, a communication system CDMA RF processor 201, a GPS RF processor 202, and a reference. A system reference clock (TCXO) 203 which provides a frequency, and an AFC 204 which is not shown but implemented as a frequency difference detector (FDD), a loop filter, and a D / A converter. In addition, the configuration of the mobile communication terminal according to an embodiment of the present invention includes a CDMA baseband processing unit 205 in charge of processing the CDMA signal. The CDMA baseband processor 205 includes a D / A converter 500 and a PDM signal counter 501 as shown in FIG. The PDM signal generated by the PDM signal generator in the CDMA baseband processor 205 is determined as the output of the PDM counter 501 of a predetermined bit. The increment of the counter is a pre-calculated value in the CDMA baseband processing unit 205, and thus it is possible to predict the frequency of the system reference clock 203 to be changed in advance, which may allow a specific register to be read out.

The GPS baseband processor 206 includes a frequency compensator 207 according to an embodiment of the present invention. In addition, the GPS baseband processor 206 may include a carrier normally controlled oscillator (NCO) 208, a correlator 209, a code generator 210, and a code normally controlled oscillator 211. It includes. In particular, the carrier NCO 208 includes a buffer register 502, an adder 503, and a phase decoder 504. In particular, the buffer register 502 may store the size of the value added to the adder 503 as a predetermined bit value, thereby changing the frequency of the generated clock. In addition, the phase decoder 504 serves to change the result value of the adder 503 into sin and cos values.

는 0.02MHz로 가정한다. 상기 GPS Carrier Tracking Loop이 Lock을 유지하고 있는 동일 시점에서 GPS Carrier NCO의 버퍼 레지스터 값은 400이고 시스템 기준시계(TCXO)의 출력 주파수가 5MHz로 가정한다. 3, 4 and 6 will be described in detail with respect to the sharing operation of the system reference clock according to an embodiment of the present invention. In the exemplary embodiment of the present invention, an arbitrary value is set and described. The arbitrary value may be flexibly changed according to the state information. The PDM counter value of the GPS Carrier Tracking Loop is locked at 2000, the output frequency of the system reference clock (TCXO) at that time is 20 MHz, and the amount of frequency change corresponding to 1 bit change of the PDM counter having a predetermined bit.

Is assumed to be 0.02 MHz. Assuming that the GPS Carrier Tracking Loop is locked at the same time, the buffer register value of the GPS Carrier NCO is 400 and the output frequency of the system reference clock TCXO is 5 MHz.

In step 605, the GPS carrier tracking loop detects that the frequency of the CDMA signal input to the mobile communication terminal is changed due to the user's movement in step 600 while the lock is held. Accordingly, in step 610, the PDM counter value is increased to match the synchronization of the frequency change of the CDMA signal inputted to the mobile communication terminal. Thereafter, step 615 of calculating a frequency change amount according to the PDM counter increase value is performed. That is, for example, assuming that the PDM counter value is increased from 200 to 2100, the frequency change amount corresponding to the difference 100 is 2 MHz. Thereafter, step 620 is performed to change the output frequency of the system reference clock with respect to the calculated frequency change amount. Therefore, stabilization according to the frequency variation of the signal of the CDMA can be performed according to the change of the output frequency of the system reference clock.

The output frequency change of the system reference clock for stabilization according to the frequency variation of the CDMA signal is changed from 20 MHz to 22 MHz as in the above-described example. Accordingly, the PDM signal counter 501 of the CDMA baseband processor 205 outputs the changed frequency value to the frequency compensator 207 of the GPS baseband processor 206. At this time, the GPS baseband processing unit 206 changes the frequency of the system reference clock while maintaining the carrier phase lock. That is, the GPS IF (Intermediate Frequency) value fluctuates as the system reference clock frequency increases by 2 MHz to 22 MHz. However, since the value of the buffer register 502 of the GPS Carrier NCO 208 is maintained at 400 (5 MHz), the GPS Carrier Tracking Loop is not kept locked. Therefore, when the frequency of the system reference clock is increased to 2 MHz, the value of the buffer register 502 of the GPS Carrier NCO 208 is calculated through Equation 1 below.

= (시스템 기준시계의 주파수 변화에 따른 GPS IF변화량) x

)(Equation 1)

= (GIF IF change according to the frequency change of the system reference clock) x

)

)0.006MHz를 구하고, 상기 구한 값 0.006MHz만큼의 GPS Carrier NCO(208)의 버퍼 레지스터(502)값을 증가시킨다. 따라서, 상기 증가된 GPS Carrier NCO(208)의 버퍼 레지스터(502)값에 의해 CDMA베이스맨드 처리부의 AFC동자과 관계없이 Lock상태를 유지하도록 하는 635단계를 실행한다. That is, the frequency change amount of the GPS Carrier NCO according to Equation 1

) 0.006 MHz, and increase the value of the buffer register 502 of the GPS Carrier NCO 208 by the obtained value 0.006 MHz. Therefore, step 635 is executed to maintain the locked state regardless of the AFC driver of the CDMA baseman processor by the increased buffer register 502 of the GPS Carrier NCO 208.

5 is a graph illustrating a frequency change amount according to the system reference clock sharing according to an embodiment of the present invention. Referring to FIG. 5, as shown in (a) of FIG. 5, the mobile communication terminal controls the frequency of the PDM signal by controlling the AFC to adjust the frequency of the CDMA response frequency and the predetermined range. To stay within. At this time, Figure 5 (b) shows the change in the GPS Carrier NCO frequency. The variation value of the frequency indicated by the reference numeral 500 shows the case where the GPS Carrier NCO Frequency is out of the error range when the frequency of the system reference clock is not compensated when the frequency of the CDMA baseband processor is changed. That is, when the GPS baseband processing unit and the CDMA baseband processing unit simultaneously operate the reference clock frequency of the GPS baseband processing unit and the CDM baseband processing unit, the PDM counter 501 changes in the AFC. The 207 may change the value of the buffer register 502 of the GPS Carrier NCO 208 so that the GPS Carrier Phase Tracking Loop may remain locked for a long time.

As described above, the configuration and operation according to the embodiment of the present invention can be made. Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications can be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but by the claims and equivalents of the claims.

Receive performance of GPS signal generated by GPS processing unit and CDMA processing unit using each reference clock or limiting GPS operation or alternating AFC operation of CDMA baseband during GPS operation. Deterioration can be reduced and the size of the terminal can be reduced accordingly.

Claims (5)

In the reference clock sharing device of a mobile terminal using a global positioning system, A communication system processing unit for processing a mobile communication system, calculating a change in frequency according to frequency variation, and outputting a calculated value according to the calculated change in frequency to a system reference clock and a GPS processing unit; Receiving a GPS signal, executing a process according to the received signal, receiving an operation value according to the frequency change amount from the communication system processing unit, executing an operation for frequency compensation according to the operation value, A reference clock sharing device of a mobile terminal for a global positioning system, comprising a GPS processing unit for compensating the frequency by the value according to the present invention. The method of claim 1, The communication system processor may further include a PDM signal controller configured to calculate a frequency change amount and output the calculated operation value to a system reference clock. . The method of claim 1, The GPS processor further includes a carrier NCO for performing a calculation for frequency compensation according to the operation value received from the communication system processing unit, and a frequency compensator for compensating the frequency according to the value calculated at the carrier NCO. A reference clock sharing device of a mobile terminal for positioning systems worldwide. The method of claim 3, wherein The carrier NCO includes a buffer register and an adder for performing an operation according to the frequency variation and storing a predetermined value according to the frequency change. In the reference clock sharing method of mobile terminals for global positioning systems, Detecting a frequency change of a communication system and comparing a magnitude of a value according to the frequency change with a predetermined reference value; Adjusting a frequency value of the system reference clock according to the comparison result; And a step of synchronizing the reference clock to a base station signal by an automatic frequency control operation.

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